In recent years, OCT that uses interference of light to image a surface morphology and internal morphology of an object is attracting a lot of attention. OCT is noninvasive to human bodies unlike X-ray computed tomography (CT) system. Therefore, application of OCT to medical and biological fields is expected. For example, OCT systems for imaging an eye fundus, cornea, or the like have already been practicalized.
In general, an ophthalmologic imaging apparatus that uses OCT performs a variety of preparatory operations before performing OCT measurement. Examples of the preparatory operations include alignment, optical path length difference adjustment, polarization adjustment, and focus adjustment. In the alignment, registration (position adjustment) of an optical system of the apparatus to a subject's eye is performed. In the optical path length difference adjustment, the difference between the optical path length of measurement light and that of reference light is adjusted to render a target site of the subject's eye in a suitable area in an image frame. In the polarization adjustment, the polarization state of one or both of the measurement light and reference light is adjusted for improving the efficiency of interference between the measurement light and reference light. In the focus adjustment, focus of the measurement light is adjusted to position the beam waist of the measurement light to or near the target site.